Electronic organ keying circuits

ABSTRACT

In a keyed-photocell type electronic organ, two or more photocells are keyed with a single, make-brake switch via two or more respective RC keying circuits having onset and/or decay times corresponding to the tone colors and/or pitches desired. Each keying circuit may control both a first photocell corresponding to a relatively low-pitched, fast-starting tone and a second photocell corresponding to a relatively high-pitched, slow-starting tone.

O United States Patent 1151 3,660,587 Martin [451 May 2, 1972 [54] ELECTRONIC ORGAN KEYING 3,291,886 12/1966 CIRCUITS 2,483,823 10/1949 2,507,884 5/1950 [72] Inventor: Daniel W. Martin, C1nc1nnat1, Ohio 3,249,678 3/1966 73 1. Assignee: r). n. Baldwin Company, Cincinnati, 01116 3,476,866

[ Filed! 1970 Primary Examiner-Lewis H. Myers Assistant ExaminerU. Weldon [21] Appl 2131 l Attorney-W. H. Breunig and l-lurvitz and Rose [52] US. Cl ..84/1.l8, 84/124, 84/126, [57] ABSTRACT [51] Im Cl Q In a keyed-photocell type electronic organ, two or more 58] l I l 13 photocells are keyed with a single, make-brake switch via two 26 f or more respective RC keying circuits having onset and/or 7 v decay times corresponding to the tone colors and/0r pitches 56] References Cited desired. Each keying circuit may control both a first photocell corresponding to a relatively low-pitched, fast-starting tone UNITED STATES PATENTS and a second photocell corresponding to a relatively highpitched, slow-starting tone. 3,124,635 3/1964 Jones et a1..... ..84/l.]8 3,249,678 5/1966 Jones ..84/1.18 4 Claims, 4 Drawing Figures C KEYlNG- Cl RCUlT K531 CJRCU Q FLUTE Pa ented'Ma 2,1972 1 I 3,660,587

2 Shoots-Sheet 1 KEYING- cmcurr H FLUTE v mvamun omaawmmn' miQQMEYS ELECTRONIC ORGAN KEYING CIRCUITS BACKGROUND OF THE INVENTION The present invention relates to realisticreproduction of organ pipe tones in a keyed-photocell or analogous type electronic organ. 7

In electrical musical instruments of the type employing electronic or electro-mechanical tone sources, it is known to employan RC circuit to control the rate of onset and/or decay of a musical tone-Examples can be found in U.S. Pat. Nos. Re. 21,137 to Firestone and 2,103,169 to Midgley. Also, taking cognizance of the fact that a speaking transient, commonly known as chiff,- starts faster than the steady-state com-. ponent of a tone, Markowitz, in US. Pat. No. 3,037,413 uses a common key switch, a diode and an RC circuit to actuate a chiff oscillator sooner than a steady-state oscillator. Since the capacitor in the chiff circuit is series-connected with the oscillator, the chili component properly decays as soon as the capacitor is charged, regardless of how long thereafter the key switch remains closed.

' It remained for the present inventor, realizing that the tone of a given organ pipe, a flute-type, starts and decays more slowly than, for example, a reed of the same pitch, to use direct current and a single key switch to cause two or more keying circuits having different time-constants to energize respectively two or more photocells, or other energy waveform-responsive means such as variable capacitors or' variable inductors. The invention applies primarily to a keyedphotocell organ of the type disclosed and claimed in US. Pat. Nos. 3,023,657 to Jones et al., and 3,249,678 to Jones. For example, an 8 ft. Reed voice may be produced via a fast time constant keying circuit, while simultaneously an 8 ft. Flute is produced, by the same key-switch,via a slower time-constant circuit. Likewise, a 2 ft. or 4 ft. Flutemay employ a fast timeconstant circuit at the same time that a 16 ft. Bourdon (Flute) may use a slow time-constant circuit; or, the same time-constant circuit may be used to key a low-pitched, fast-starting tone (for example, a Reed) at the same time as a relatively high-pitched, slow-starting tone (for example, a Flute). By optimizing the use of the time-constant circuits, as few as two may sufiice for both the different timbres and the different footages actuated via a single key switch. Thus the present invention provides means for achieving adequate simulation of organ pipe tone envelopes in a system of the type disclosed in the aforesaid Jones et al and Jones patents.

SUMMARY OF THE INVENTION In accordance with the present invention, realistic simula-,

tion of organ pipe tone envelopes is achieved by optimum utilization of two or more time-constant circuits of different rise times and different decay times. A single key switch for a given key actuates, from a direct-current source, at least two DC-actuable photocells having impedances which are modified by light energy to produce tones having characteristics appropriate for the tone pitches corresponding to the actuated key and the particular tone colors desired. Also, lowpitched, fast-starting tones of one tone color and high-pitched, slow-starting tones of another tone color can be produced via a single keying circuit.

BRIEF DESCRIPTION OF THE DRAWINGS The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of one specific embodiment thereof, especially when taken in conjunction with the accompanying drawings, wherein: 7

FIG. 1 is a broken, diagrammatic (and partly schematic) view of the main components of the type photoelectric organ to which this invention applies;

FIG. 2 is a part-block, part-schematic circuit diagram of a keying system for a photoelectric organ in accordance with this invention;

FIG. 3 is a schematic circuit diagram illustrating the details of the system of FIG. 2; and

FIG. 4 is a plan view of a portion of a photocell array as employed with this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION Referring to FIG. 1 of the accompanying drawings, the Jones-type photoelectric organ, to which this invention is particularly applicable, comprises a light source (not shown),

' radiation from which falls upon a rotating pitch disc 1. Con- '15 and 17, across which is deposited a layer 19 of photosensitive material, for example, lead sulphide. The physical layout of a photocell array is further described hereinafter in connection with FIG. 4, while the details of operation of the present invention are discussed with reference to FIGS. 2 and 3.

Referring now to FIG. 2, a simple, make-break key switch 2 having a pair of contacts actuated by a playing key 4 of a conventional keyboard (not shown), switches direct current from a source B+ to a fast keying circuit 6 at the same time as it switches 13+ to a slow keying circuit 8. Multiple output connections of fast keying circuit 6 are directed to one photocell electrode (13 in ,FIG. 1) in each of plural arrays of the type described in FIGS. 1 and 4, the arrays being indicated in FIG. 2 on disc 11a as 8 ft. Reed, 4 ft. Reed, 2 ft Flute and. 1 ft Flute. The multiple output leads from the slow keying circuit 8 are directed to plural photocell arrays indicated as 16ft. Bourdon, 4 ft. Flute and 8 ft. Flute. Thus, from a single key switch'2, photocells for both relatively fast-starting tones and relatively slow-starting tones are energized by DC from source B+. In the interest of simplicity of FIG. 2, the light source, pitch disc 1, waveform disc 21 and output system for the photocells are omitted. FIG. 2 also contains a chiff keying circuit 9 which is the subject of an invention disclosed in copending US. Patent Application Ser. No. 21,815 of W. C. Wayne, Jr. and Albert Meyer, filed Mar. 23, 1970, and assigned to the same assignee as the present application.

Reference is now made to FIG. 3 of the drawing, wherein are illustrated the details of a keying system for two adjacent semitones of a keyboard (for example, a Swell manual), in accordance with the invention. A playing key 10 of a conventional keyboard (not shown), corresponding to note C (middle C at 8 ft pitch) selectively actuates a key switch 12 having a connection to a DC source 14 and a connection to a clicksuppressing resistor 16 of low resistance, the latter in turn being connected to a plurality of keying or time-constant circuits illustrated as CKC (C FKC (C and SKC (C4).

representing, respectively, chiff keying circuit," fast keying circuit and slow keying circuit, for the note C Dashed lines enclose those elements of the several keying circuits which can be considered part of the keying circuits themselves. The slow keying circuit SKC (C is comprised of a diode 23 polarized to conduct current from source 14 and feeding a shunt resistor 18 and series resistor 20, with a shunt capacitor 22. A series resistor 24 and a second shunt capacitor 26 are connected across capacitor 22, and a shunt resistor 28 is connected across capacitor 26. Resistors 20 and 24 are bypassed by a diode 30, polarized oppositely to source 14. The fast keying circuit FKC (C is comprised of a shunt resistor 33 and series resistor 34, across which are parallel-connected shunt capacitor 36 and shunt resistor 38. The chifi' keying circuit CKC (C is fed by diode 83, polarized in conducting relationship with source 14, and is composed of series-connected in series and across resistor 42, and a diode 48 connected across capacitor 46 to ground and polarized oppositely to source 14. At point 49 there are also a load resistor 51 to ground and a shunt connection through resistor 50 to a second DC source 52. v

The output lead 56 of SKC (C carries the slow starting DC keying voltage to the C photocell pair on two 8 ft arrays, two photocell pairs being schematically illustrated at 58 and 60. Output lead 56 also is connected to cell 68 via diode 66.

A portion of a typical photocell array is shown pictorially in FIG. 4, wherein a glass substrate 51 (for mounting on stationary disc 11a, FIG. 1) has deposited thereon a metallic circuit pattern composed of the interdigitated portions 13, 15, 17 which respectively comprise the keying electrode 13 and two collecting electrodes on one photocell pair as described in FIG. 1. The photosensitive material comprising the strip 19 is deposited, as shown, on the metallic pattern composed of electrodes 13, 15, 17, etc. As described in detail in the aforementioned Jones and Jones et al patents, the resistance of the deposit 19 between electrode 13 and its neighbors 15 and 17 is varied by modulated illumination produced by rotating over variable-area waveform patterns, not shown. Keying voltage is supplied to electrode 13 via a lead 61, while modulated signal will be collected from electrodes 15 and 17 by leads 63 and 65, respectively.

Referring again to FIG. 3, the output signals from photocells 58, 60 and 68 are passed to opposite terminals of the primary windings of DC-canceling transformers 62, 64 and 70, respectively, the center taps of which are grounded. The secondary coils of the transformers are connected at one end to ground and at the other end, via stop control switches 72, 74, and 76,

respectively, to a common output lead 78 feeding an output amplifier 80 and loudspeaker 82, the latter being representative of any suitable, conventional, electroacoustic translating system. The output lead 56 of the slow keying circuit can also be connected, as at point 84, to photocell-pairs C and C in 4 ft and 16 ft photocell arrays, respectively, in the event that it is desired to actuate, such cells from the slow keying circuit. Also, there is shown a connection at point 86, via diode 88, to a chiff keying circuit for the note B This means that the pitch corresponding to the note C would be proper to accompany a B note in order to provide a chiff component, as will be explained in detail hereinafter in connection with CKC (C,,).

In operation, when key switch 12 (FIG. 3) is actuated by depression of key 10, DC voltage from source 14 is applied across resistors 16 and 18 in series. The potential across resistor 18 in SKC is applied to capacitor 22 via resistor 20, and the voltage across capacitor 22 builds up slowly. This voltage is applied to capacitor 26 via resistor 24. The comparatively slowly rising voltage at the output lead 56 is applied to the cells connected thereto and the voltage drop produced in the cells is modulated by the varying light energy impinging upon them. The alternating components of the tone signals from the two parts of each photocell pair are additive in a center tapped transformer, because the waveform patterns, as at 5 and 7 in FIG. I, are purposely disposed 180 out of phase. On the other hand, the DC component from each portion of a photocell pair oppose each other in the grounded center-tap primary winding of each transformer and thus cancel. Upon opening of key switch 12, the decay time of the control voltage on lead 56 and hence of the tone signals is hastened by the presence of diode 30 and comparatively low resistor 18 which act to discharge capacitor 26 rather than relatively high resistor 28 above.

The output lead 90 from fast keying circuit FKC (C is connected to two 8 ft cells 92 and 94 and to a 2 ft cell (not shown) representing note C,,. There is also shown a connection via 36, the latter of which is charged via resistor 34 from the DC source'14 upon actuation of switch 12. The rate of charge of capacitor 36 is dependent upon the time constant of the capacitor in combination with the Thevenin equivalent resistance of resistor 34 in parallel with resistor 38 and the I photocell loads. The voltage drop appearing across resistor 38 is applied to output lead 90 to energize the photocells con- },nected thereto. The build-up and decay rates of circuit FKC (C are relatively fast compared with the slow keying circuit SKC (C During decay, resistor 33, speeds the rate of discharge of capacitor 36.

The chiff keying circuit CKC (C,), which is the subject of the aforementioned co-pending U. S. Patent application by Wayne, Jr., et al., provides the proper DC keying voltage to produce both a rapidly rising and rapidly decaying tone control envelope, even though key switch 12 is held closed. The photocell actuated by such a pulsed envelope produces a characteristic chiff sound at the beginning of any tone requiring a chiff component. The output lead 98 of the chiff keying circuit is connected via point 100 and a diode 54 to a chiff photocell-pair corresponding to the note F This produces a pitch which is somewhat greater than five times the fundamental frequency of a note corresponding to C,. It is known in the art that such a frequency relationship exists between the main chiff component and the fundamental component of the tones of certain stops, notably stopped flutes. The chiff keying circuit output lead 98 is also connected, via a scaling voltage divider (comprising resistors R and Ry) and diodes 102 and 103, to a G 8 ft. Diapason photocell-pair and to the F Diapason cell-pair, respectively, to supply other characteristically high chiff components required. Output lead 98 also has a connection to diode 104, which is connected to the 4 ft Orchestral Flute photocell-pair 106 for note C (From this point there is also a diode 108 connected to the fast keydiode 96 to an Orchestral Flute (4 ft.) cell (not shown) cornote C Thus the 4 ft Orchestral Flute tone corresponding to the playing key 10 for C, has a fast-starting, steady-state component supplied by the C: cell via diode 96, with a sub-harmonic chiff component (at the C pitch) via diode 104.

The operation of the chili" keying circuit CKC (C is more involved than that of the previously described keying circuits. Initially, with key switch 12 open, diode 48 is turned on clamping point 49 to a slightly negative level (the drop across diode 48) andcutting off diode 54. However, when the key switch 12 is closed, the voltage at point 49 becomes more positive as capacitors 44 and 46 commence charging via resistor 40. This voltage level at point 49 is momentarily sufficiently positive to cut off diode 48 and turn on diode 54, thereby gating on chiff photocell F and all of the cells connected to output lead 98. These cells are thus able to produce tone signals depending upon the rate at which they are modulated by light energy impinging thereon, as explained hereinbefore. Capacitor 44 charges quickly after which source 52 regains control, clamping the voltage at point 49 to a slightly negative voltage level, equal to the forward drop across diode 48. The momentary chiff components thus decay even though key switch 12 is held closed. When key switch 12 is opened, capacitor 44 rapidly discharges through resistor 42 and diode 48, and the circuit is reset for another actuation of key switch 12. A chiff tone is not elicited when key switch 12 is opened because point 49 remains clamped to ground as explained above.

The fifth-partial chiff effect can be turned on or ofi by the not too critical so that two or more adjacent notes may use the same chiff frequency), isolating diodes 83 and 85 must be inserted at the input terminal for each commonly used CKC circuit.

A second key 110, of the same keyboard as key 10, actuates a second key switch 112 corresponding to the note C Switch 112 in turn transmits DC from the source 14 to three keying circuits represented in block form at 114, 116 and 118, which may be similar in characteristics to the keying circuits already illustrated in detail. The output signals of respective keying circuits 114, 116 and 118 are shown connected similarly to photocells as the output signals on the hereinbefore described output leads 98, 90 and 56. It is not believed necessary to describe this circuitry in detail.

The present invention has been applied to a photoelectric organ in such a way that two or more tones and/or voices having different rise and/or decay times can be derived concurrently via s single key switch that is, a simple make-break switch having a pair of contacts. Also, it has been shown that a single RC-time-constant circuit has been used both for a relatively low-pitched, fast-starting (reed type) tone and for a relatively high-pitched, slow-starting (flute-type) tone. Furthermore, it will be obvious to one skilled in the art that the utility of this invention is not limited to photoelectric organs. The teachings may be applied to any waveformreproducing type of electric organ in which the means for producing the tone signals can be polarized and/or actuated from a direct current source.

While I have described and illustrated one specific embodimentof my invention, it will be clear that variations of the details of construction which are specifically illustrated and described may be restored to without departing from the true spirit and scope of the invention as defined in the appended claims.

lclaim:

l. A photoelectric organ, said organ including a stationary array of photoelectric cells each pertaining to a different tone timbre and tone pitch, said tone pitches being octavely related, a scanning tone disc having recurrent circles of transparent slots spaced for separate radii of said discs to provide different tone pitches at different radii, a stationary timbre disc located between said scanning tone disc and said array of photocells and having a circle .of timbre producing trans parencies located between each circle of slots of said scanning tone disc and a photocell of said array of photocells such that light passing from any circle of slots will pass through a circle of timbre producing transparencies and fall ultimately on one of said photocells as said tone disc scans, each of said photocells including two collecting electrodes separated from a keying electrode by a layerof photoresistive material, a center grounded primary winding connected across each two collecting electrodes of each photocell, a separate secondary winding coupled to each of said primary windings, output bus means, and tab switches connecting said secondary windings to said output bus means, and a loud speaker separately coupled to said output bus means, a key switch, a voltage supply, a keying lead, means connecting said kev switch to convey voltage from said voltage supply to said keying lead, plural diverse RC tone envelope control circuits connected in parallel with each other to said keying lead; and means connecting said envelope control circuits each to plural ones of said keying electrodes, said RC tone envelope control circuits having diverse attack and decay rates appropriate to diverse timbres of a pipe organ.

2. The combination according to claim 1, wherein said RC tone envelope control circuits are three, a first sufficiently slow to be appropriate to an 8 ft flute tone, another sufficiently fast to be appropriate to a 1 ft flute tone and a reed tone, said tones being of pitches which are octavely related, and athird having sufiiciently fast rise and an immediately following decay to be appropriate to a chifl component of a tone.

3. The combination according to claim 2, wherein said first RC tone envelope control circuit is connected to control a 16 ft Bourdon, an 8 ft flute, a 4 ft flute tone, wherein said another RC tone envelope control circuit is connected to controla 2 ft flute, a 1 ft flute and a 4 ft reed tone, all said tones being of pitches which are octavely related and an 8 ft reed tone.

4. In a photoelectric organ, a plurality of photoelectronic tone sources grouped to include in one group a 2 ft flute, a 1 ft flute, and a 4 ft reed, and an 8 ft reed of a given common nomenclature, in a second group a 4 ft flute, an 8 ft flute and a 16 ft Bourdon of said given common nomenclature, in a third group a chiff generator of pitch appropriate to the tones of said first and second groups, a slow keying circuit common to said first group and having an attack and decay time appropriate to the tone generators of said first group, a fast keying circuit common to said second group and having an attack and decay time appropriate to the tone generators of said second group, and chiff keying circuit having attack and decay times appropriate to chiff components of said first and second .groups of tones, a single key operated means for commonly energizing all said keying circuits, and separate tab switches connected between each of said tone sources and a common output load. 

1. A photoelectric organ, said organ including a stationary array of photoelectric cells each pertaining to a different tone timbre and tone pitch, said tone pitches being octavely related, a scanning tone disc having recurrent circles of transparent slots spaced for separate radii of said discs to provide different tone pitches at different radii, a stationary timbre disc located between said scanning tone disc and said array of photocells and having a circle of timbre producing transparencies located between each circle of slots of said scanning tone disc and a photocell of said array of photocells such that light passing from any circle of slots will pass through a circle of timbre producing transparencies and fall ultimately on one of said photocells as said tone disc scans, each of said photocells including two collecting electrodes separated from a keying electrode by a layer of photoresistive material, a center grounded primary winding connected across each two collecting electrodes of each photocell, a separate secondary winding coupled to each of said primary windings, output bus means, and tab switches connecting said secondary windings to said output bus means, and a loud speaker separately coupled to said output bus means, a key switch, a voltage supply, a keying lead, means connecting said key switch to convey voltage from said voltage supply to said keying lead, plural diverse RC tone envelope control circuits connected in parallel with each other to said keying lead; and means connecting said envelope control circuits each to plural ones of said keying electrodes, said RC tone envelope control circuits having diverse attack and decay rates appropriate to diverse timbres of a pipe organ.
 2. The combination according to claim 1, wherein said RC tone envelope control circuits are three, a first sufficiently slow to be appropriate to an 8 ft flute tone, another sufficiently fast to be appropriate to a 1 ft flute tone and a reed tone, said tones being of pitches which are octavely related, and a third having sufficiently fast rise and an immediately following decay to be appropriate to a chiff component of a tone.
 3. The combination according to claim 2, wherein said first RC tone envelope control circuit is connected to control a 16 ft Bourdon, an 8 ft flute, a 4 ft flute tone, wherein said another RC tone envelope control circuit is connected to control a 2 ft flute, a 1 ft flute and a 4 ft reed tone, all said tones being of pitches which are octavely related and an 8 ft reed tone.
 4. In a photoelectric organ, a plurality of photoelectronic tone sources grouped to include in one group a 2 ft flute, a 1 ft flute, and a 4 ft reed, and an 8 ft reed of a given common nomenclature, in a second group a 4 ft flute, an 8 ft flute and a 16 ft Bourdon of said given common nomenclature, in a third group a chiff generator of pitch appropriate to the tones of said first and second groups, a slow keying circuit common to said first group and having an attack and decay time appropriate to the tone generators of said first group, a fast keying circuit common to said second group and having an attack and decay time appropriate to the tone generators of said second group, and chiff keying circuit having attack and decay times appropriate to chiff components of said first and second groups of tones, a single key operated means for commonly energizing all said keying circuits, and separate tab switches connected between each of said toNe sources and a common output load. 